A need exists for a safe and efficient liquid level measuring device for underground bulk storage tanks for gasoline in service stations and other like environments. Customarily, measurements are made with long measuring sticks to determine the liquid level in underground tanks before and/or after filling. Such traditional procedure requires removing the tank cover which creates a safety hazard due to the possible escape of fumes and requires the service station attendant or manager to leave his office post and to devote full time and attention to the tank filling operation and inventory procedure. All of this is costly, dangerous and inefficient.
The objective of the invention is to satisfy the above-stated need for a more efficient, reliable and safer means for selectively measuring with accuracy the liquid levels in a plurality of remote underground bulk storage tanks, by means of a single instrument and associated selector valve and manual pump mounted as a compact unit in the office of a service station or the like. The arrangement enables an attendant to accurately inventory the gasoline or other bulk liquids in multiple underground tanks without leaving the office with its attendant duties and without even exposing himself to the weather outside of the office. A simple multi-way selector valve communicating through tubes with plural underground tanks is coupled with a single liquid level measuring gage of the type disclosed in U.S. Pat. No. 3,688,577. The face of the measuring instrument is calibrated preferably in inches of liquid, so that a direct inventory of the liquid content of each of several remote underground tanks may be logged. The bellows of the single measuring instrument is pressurized with atmospheric air by operation of a simple elastic bulb pump equipped with a one-way check valve so that air can be drawn into the bulb and pumped to the instrument and the selected storage tank by the attendant until a proper pressure balance is reached. This condition will be known to the attendant when the instrument pointer falters. The liquid content in the particular tank in terms of liquid depth in inches or other linear measure may then be directly read.
An important advantage which the invention offers over conventional haphazard measuring practices is to reduce and eliminate the hazards of overfilling tanks with volatile products. The attendant can have a visual read-out at the instrument during the actual filling process in terms of "inches of the product" in the tank. Furthermore, the ability of the system to monitor up to three tanks which may be located as much as 75 feet away from the monitoring station is obviously a great advantage in terms of efficiency and economy.
Other features and advantages of the invention will become apparent during the course of the following detailed description.